This invention relates to apparatus for removing gelatinous sludge and solid sedimentations from settling basins, lagoons, ponds, pools, and the like.
In clarifying raw water from natural sources, such as lakes, rivers, wells and the like, to yield potable water, it is the usual practice to add to the raw water coagulants, such as alum with or without an alkali, such as lime and/or a synthetic coagulant, such as poly acrylamides. As is well known in the art to which our invention relates, these additives provide nuclei which attract the fine suspended solids of coloidial size or larger so as to form macroscopic agglomerations, which, with quiescence, tend to settle from the water. Also in clarifying industrial or other water for recirculation or for stream or sewer disposal it is common practice to facilitate solids separation from the liquid media by providing a zone or zones of quiescence. The sludges so formed and so deposited in the lower levels of the receptacle tend to gel, coalesce, thicken or cement themselves to each other and thus resist withdrawal through bottom outlet means which may communicate with suitable suction means, such as a pump. Dredging is an effective means for removing such sludge but is an expensive operation, results in excessive turbulence and involves the withdrawal of relatively large volumes of water. Some settling basins or clarifiers are equipped with drags, rakes, plows, scrapers, and the like, to move the sludge to withdrawal points, but such equipment is expensive to purchase and maintain. Other apparatus employed for such solids removal consists of intake or suction boxes which are moved along the bottom of the settling basin by mechanical means, but such devices are expensive to install, are adaptable only to basins of rectangular or circular shape, as viewed in plan, and require flat or relatively flat bottoms in the basins in which they are employed. Decantation of supernatent fluid and air drying of the sludge are not practical since they involve extended periods of time and atmospheric conditions conducive to evaporation.
Heretofore, it has been the usual practice to dispose of such gelatinous sludges accumulated in settling basins by flushing the same into surface streams or by discharging the gelatinous sludge to drying beds. Due to the pollution of surface streams, it is very desirable to remove these solids from settling basins by means other than flushing such solids to streams. While some water filtration plants have the large areas required for drying such gelatinous waste, many plants do not have such large areas.